Method of making superphosphates.



No. 655,458. Patented Aug. 7, I900. H. SAXL.

METHOD OF MAKING SUPEBPHOSPHATES.

(Application filed Dec. 26, 1899.)

(No Model.)

| r as co Paoruuma, WASHINGTON n c UNITED STATES PATENT OFFICE.

IIEINRICII SAXL, or sAN FRANCISCO, CALIFORNIA, AssIeNoR on ONE-HALF TOAARoN A. ADLER, or SAME PLACE.

METHOD OF MAKING suPERPHosPHA' Es.

SPECIFICATION forming part of Letters Fatent Nb. 655,458, dated August'7, 1900.

Application filed December 26, 1899. Serial No. 741,589. (No specimens.)

T0 at whom it may concern:

Be it known that I, HEINRICH SAXL, a subject of the Emperor ofAustria-Hungary, residing in the city and county of San Francisco, Stateof California, have invented an Improvement in the Manufacture of Super-Phosphates; and I hereby declare the following to be a full, clear, andexact description of the same.

The object of this invention is to provide a concentrated easily-solublephosphoric acid and the production of super-phosphates rich infertilizing material.

It consists, essentially, in a process and treatment of super-phosphatesas usually produced, whereby I am enabled to produce a product which isthree or four times stronger and more concentrated than by the usualmethods.

In preparing super-phosphates it is usually efiected by mixing sulphuricacid with the raw product, such as bone, bone-meal, bone-ashes, spodium,also apatite, coprolite, and phosphorite, and generally naturalphosphates which appear in lime-bearing rocks and the like, or any ofthe phosphates-of-lime and phosphoric acid containing material. Thesulphuric acid acts upon the material and disengages phosphoric acid,whichin this state is easily soluble; but as the lime takes up a veryconsiderable quantity of sulphuric acid it requires about an equalquantity, in weight, of the material and the sulphuric acid to producethe soluble phosphoric acid. Gonsequently as ordinarily produced onlyeighteen or twenty per cent. of easily-soluble phosphoric acid containedin the super-phosphate is the result.

The accompanying drawing illustrates a form of apparatus by which myprocess can be carried out.

In carrying out my process any raw product, such as previouslymentioned, containing phosphate of lime is first ground or pulverized bya suitable mill (not here shown) and is then introduced into a mixer, aform of which is illustrated at A, consisting of an exterior tank orchamber with a rotary shaft and stirring-arms. 2 is a vessel containingsulphuric acid which may be of a strength of about 50 Baum. Theproportion of acid is about 1.60 of acid to one part of phosphate oflime. The acid and phosphate-of-lime-bearing material are stirred andagitated in the mixer A for a suflicient time and then removed and leftupon a floor for from fortyeight to seventy-two hours or more, until theacid has had its full efiect upon the mass. This separates thephosphoric acid from the material in which it was originally contained.After the mass has thus remained for a suflicient time it is placed in asecond mixer 3,with about two parts of-water to one of the material, andis there stirred for two or three hours, more or less, then allowed tosettle, and the clear liquid can be drawn 0% into an evaporator,(shownat 4). This evaporator may be of any suitable well-known construction.(Not here shown.) The sulphate of lime re maining in the mixer 3 can bewithdrawn by means of a movable bottom 5 or in any other suitablemanner. Within the evaporator 4 the liquid is evaporated to about 20Baum, and I then add fifty per cent. of raw material. This may beconveniently introduced througha funnel, as shown at 6, or by anysuitable means. The mixing of the fresh raw material with theconcentrated acid already within the evaporator causes the separation ofmore phosphoric acid from the raw mate rial, and this is united with theportion already in the apparatus. After this has been effected themixture is drawn off through a suitable discharge 7 into a tank orreceiver 8, where the heavier solid portion again settles, and theliquid is drawn off and again returned to the evaporator 4, where it isthen evaporated to about eighty-five or ninety-five per cent. ofstrength. I then add about fifty per cent. of new material. Thisproportion will be variable because it depends entirely upon thepercentage of phosphate of lime contained in the material, some gradeshaving more than others. .Anyphosphorie acid which is still contained inthe residue which has been withdrawn from the mixer 3 may be expressedor separated therefrom by filtering, centrifugal, or other well-knownmeans. A certain amount of residue will be carried by the liquid whichis withdrawn from the mixer 3, and while subjected to the heat of theevaporator is separated in the liquid, and

when the whole is discharged from the evaporator into the settlingapparatus (represented at 8) this residue will be settled and separatedfrom the liquid. This residue may also be subjected to a similar processto that above described to deprive it of any valuable liquid which mayremain in it- The liquid thus obtained can then be added to that whichis in the evaporator 4. The remaining residue after all possible liquidhas been separated therefrom may then be dried and mixed and will yielda good fertilizer in itself. If, however, it is not desirable to subjectthe residue from the mixing and settling apparatus 3- or 8 to theoperation of separating the phosphoric acid contained in it, thisresidue will form a good high-grade super-phosphate by drying withoutfurther treatment.

' It is to be understood that as many of the different forms ofapparatus may be employed as will be necessary to enable the work to becarried on continuously.

One advantage gained by this operation is that by the use of theconcentrated sulphuric acid in excess in the place of dilute sulphuricacid which has heretofore been used I avoid the formation of acidphosphate and obtain the greatest possible separation of the lime in theform of sulphate of lime. I am also enabled to almost entirely avoidleaching,and thereby the solution of gypsum, lime, and other foreignsubstances which would other. wise enter into the solution of phosphoricacid and prevent high concentration. In this process I save a largepercentage of the sulphuric'acid which has formerly been necessary, andit is the only described process of which I am aware in which phosphoricacid of from eighty-five to ninety-five per cent. can be produced andthe resultant high-grade super-phosphate of from sixty-five toeightyfive per cent. 7

It will be understood that various forms of apparatus may be used incarrying out my invention. The liquid may be separated from the masseither by settling, as herein stated, or by filters, by air-pressure,centrifugal force, or any suitable or desired means,which I do notespecially claim.

Having thus described by invention, what 1. In the manufacture ofsuper-phosphate, the steps consisting in first producing a normalsuper-phosphate by subjecting the phosphate-of-lime-containing materialto the action of sulphuric acid, then mixing the mass with about twoparts of water to one of material, then separating the liquid from themass and evaporating it, then mixing with the product a second body ofphosphate-of-lime containing material, and withdrawing the re sultantmass and separating the liquid therefrom.

2. In the manufacture of super-phosphate, the steps consisting in mixingthe pulverized phosphate-containing material with concen-v ,5 I claim asnew, and desire to secure by Letters Patent, is

trated sulphuric acid, allowing the massto HEINRICH SAXL.

WVitnesses:

S. H. NOURSE, JESSIE O. BRODIE'.

